A wide variety of signal lights serving many different purposes are found in road vehicles, in railway signals and in street traffic signals. In each of these situations, a light source, such as a vehicle lamp or railway signal lamp or traffic light lamp, must be electrically connected to a power source via some type of electrical connection. Because the large number of electrical connections may be included in a single signal lamp, a small savings in cost per electrical connection can translate into a significant savings for the overall vehicle cost. Costs also result as each light source having an electrical connection requiring assembly and installation into the vehicle signal lamp or other signal lamp which then must be assembled into the vehicle or signal apparatus and connected to a power source. Each of these steps adds time, complexity and expense to the manufacturing process. As such, a reduction in the number of parts and steps needed to accomplish assembly and connection of a signal lamp causes a direct impact on lowering the manufacturing time and costs.
Reducing light device electrical connection costs is not easy due to a number of constraints that confront the light device electrical connection field. Throughout the design and manufacturing process quality is an important consideration. The light device electrical connection must be sufficiently robust that the electrical connection performance is not degraded by mishandling during manufacture, shipment and assembly processes. Depending on the application, electrical connections must function reliably under severe operational conditions such as severe shock and vibration, a wide range of temperature, and exposure to water, oil and dirt.
Additional constraints are specific to the vehicle light device field. The engine compartment and surrounding space increasingly has been filled by various other components putting space at a premium. A wire harnesses tends to be bulky and difficult to manipulate within tight spaces. This is a significant disadvantage when the wire harness is to be used in the increasingly limited space of modern vehicles. Therefore vehicles present an enhanced design problem in the areas of sufficient space and in installing the wire harness into the designed space.
These design and manufacturing problems can contribute to reduced reliability of light device electrical connections. Where the space of installation of the wiring harness is cramped, assembling the wire harness into the vehicle can result in poor engagement of the wire harness plugs. When subjected to normal shock and vibration, the plugs can then become disengaged. While locking tabs on plugs may be used to prevent disengagement, this adds additional material and additional steps to the manufacturing process resulting in plug components being even more expensive. Further, the difficult manipulation of the wire harness in a cramped area may subject the internal wires to stresses resulting in breakage of the wires or a loss of connection between the wires and the plugs.
The difficult manipulation of the wire harness in a cramped space can increase the potential for creation of an electrical short. The wire harness will frequently be in contact with other surfaces once installed in a vehicle. As the vehicle is shocked and vibrates, the wire harness will rub against the other surfaces, fraying the insulating material. A breach of this insulation presents a substantial risk of electricity arcing from the exposed wire to other parts of the vehicle. Of course, a more robust insulation results in a bulkier wire harness, presenting increased manufacturing and design costs.
Recently, vehicle lamps, railway signal lamps and traffic signal lamp have begun to employ light emitting diodes LED as a light device to replace the incandescent light bulbs. This application of LEDs has allowed the use of several LEDs on a circuit board to replace a single light bulb with multiple LED's and multiple light bulb with a number of LED's The advantage provided is that if one of the several LEDs ceases to operate, the other LEDs contained in the vehicle lamp will continue to illuminate and the signal or warning purpose of the lamp will continue to be served. This use of multiple LED's, while reducing the costs associated with incandescent lights presents another set of costs associated with the installation of multiple LEDs onto a circuit board.
It is desirable, therefore, to provide a light device electrical connection for a signal lamp that is inexpensive and simple to manufacture. It also is desirable that the light electrical connection be easily installed into a vehicle or signal instrument such as a railway signal or a traffic signal. It would be desirable that the light device electrical connection provide reliable operation in a wide range of environmental conditions including shock, vibration, and in the presence of oil, dirt and water, and in temperature extremes. The light device electrical connection also should be easily configured to fit within space confines of a variety of vehicle designs while minimizing the risk of electrical shorts.